A year of discoveries about monkey malaria

Malaria isn’t just a disease of people. Over 200 species of Plasmodium have been described infecting different vertebrates including rodents, birds, reptiles, and monkeys.

Last month Liu et al described the evolutionary origins of P. falciparum, the deadliest of human malaria parasites, which arose from a zoonotic (animal to human) transmission of a gorilla parasite. Before the general belief was that P. falciparum and its related simian parasites diverged at the same time as the ancestors of humans and chimpanzees did so.

Why do we care about monkey malaria? Animal reservoirs of human parasites renders the possibility of malaria eradication near impossible as the risk of reintroduction looms.  So even if falciparum arose from a single or few chance events thousands of years ago, the key question remains: Are ape populations a source for recurring human infection?

Scientists, using molecular assays,  reported gorillas infected with P. falciparum in Gabon. However, the samples were from captive animals, though originally born in the wild, living on an island sanctuary. Whether the finding represents a reverse-zoonotic event from exposure to humans or if the infection can be maintained in the wild is of critical importance. In the latest issue of Emerging Infectious Diseases we seem to have an answer. A survey of wild chimpanzees living in an undisturbed tropical rainforest habitat found five parasites including the human Plasmodia species malariae, vivax, and ovale.

While local elimination in many settings may be feasible, it seems that malaria is here to stay.



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